using System.Collections.Generic;

namespace TodoApplication
{

    public interface ICom<TItem>
    {
        void Do(List<TItem> Items);
        void Undo(List<TItem> Items);
    }

    public class Adding<TItem> : ICom<TItem>
    {
        private TItem items;

        public Adding(TItem item)
        {
             item = items;
        }

        public void Do(List<TItem> Items)
        {
            Items.Add(Items);
        }

        public void Undo(List<TItem> Items)
        {
            Items.Remove(Items);
        }


    }

    public class Removing<TItem> : ICom<TItem>
    {
        private TItem items;
        private int index;

        public Removing(TItem item, int ind)
        {
            items = item;
            index = ind;
        }

        public void Do(List<TItem> Items)
        {
            Items.Add(items);
        }

        public void Undo(List<TItem> Items)
        {
            Items.RemoveAt(index);
        }
    }
    public class ListModel<TItem>
    {
        public enum Action
        {
            Pop,
            Push
        }

        private class HistoryUnit
        {
            public Action RealAction;
            public TItem Item;
            public int Index;
        }

        public List<TItem> Items;
        public int Limit;
        private LimitedSizeStack<HistoryUnit> actionHistory;
        public ListModel(int limit)
        {
            Items = new List<TItem>();
            Limit = limit;
            actionHistory = new LimitedSizeStack<HistoryUnit>(limit);
        }

        public void AddItem(TItem item)
        {
            var command = new HistoryUnit { RealAction = Action.Push, Item = item, Index = Items.Count };
            actionHistory.Push(command);
            Items.Add(item);
        }

        public void RemoveItem(int index)
        {
            var command = new HistoryUnit { RealAction = Action.Pop, Item = Items[index], Index = index };
            actionHistory.Push(command);
            Items.RemoveAt(index);
        }

        public bool CanUndo()
        {
            return actionHistory.Count != 0;
        }

        public void Undo()
        {
            var command = actionHistory.Pop();
            if (command.RealAction == Action.Pop)
                Items.Insert(command.Index, command.Item);
            else
                Items.RemoveAt(command.Index);
        }
    }
}